Diagnostic methods for time-resolved optical spectroscopy of shocked liquid deuterium

Abstract

Sandia National Laboratories Z facility generates shocks in liquid deuterium with pressures up to 100 GPa. Temperature measurements using spectroscopy of the shocked $D_2$ self-emission can help discriminate between different deuterium equation of state models. Time-resolved spectra are recorded using four diagnostic systems, each composed of a fiber optic probe that transmits light from the shocked $D_2$ to a remote streaked spectrometer. Calibration of the entire system in the streaked mode is performed using a xenon arc lamp. The absolute xenon arc lamp spectrum is determined by comparison with National Institute of Standards and Technology (NIST) standards. Data analysis is performed by measuring the wavelength-dependent efficiency for each system and applying this to determine the shocked $D_2$ self-emission spectrum. Temperature is deduced from either the wavelength dependence of the spectral radiance, ignoring the absolute intensity, or from both the wavelength dependence and the absolute intensity. The shocked $D_2$ temperature uncertainties obtained with the methods described here are well below the differences between $D_2$ equation of state (EOS) models and these measurements should therefore provide new insight into $D_2$ EOS physics.